K. Poudel, S. Dahal, B. M. Dahal
, S. Gurung
Abstract
Budhi Khola of Ithahari and Singhiya Khola of Biratnagar are the main rivers flowing through these two big municipalities. These municipalities are chosen due to the increasing concern of water quality deterioration increasing urban area and solid and liquid waste. Both municipalities have experienced a rapid urban development in the Terai region and in order to assess the present condition and possible future scenarios of the rivers flowing through these municipalities, the study has been assessing the water quality status by applying different methods.
The major objective of the study is to assess the ecological impacts on river water quality in Eastern Terai Region. Physico-chemical analysis were conducted to indicate the status of water quality, oxygen relationship in water, atmospheric reaeration in water, PH, Temperature and conductivity of water and behavior of Phosphate, Nitrate and Ammonia in water. Biological assessment of the rivers was conducted to evaluate the ecological impacts of pollution from various points and non- point sources using NEPBIOS score method. The study showed that these rivers are heavily affected by human activities. The growing number of settlements and increasing amount of solid waste and waste water are found to be the main causes of water pollution.The physicochemical analysis of the water showed that the rivers are within acceptable range. However, the higher values are recorded around the pollution discharge and industrial effluents areas.
Introduction
Anthropogenic induced river water deterioration is becoming an increasing concern in many parts of the world (UNESCO, 2010) with urbanization being recognized as one of the major contributing factors (Cuffney et al., 2008; Roy et al., 2009). It results in the “alteration of landscape from natural to residential, commercial and industrial uses, through construction” (Wheeler et al., 2005). An
Department of Environmental Science and Engineering, Kathmandu University, Dhulikhel, Nepal
Corresponding Address: [email protected], [email protected]
investigation in Hindu Kush-Himalayan countries also highlights four major deteriorating factors for river water: waste, land use, damming/impoundment and climate change (Korte, 2009).
In Nepal also, the trend of urbanization is increasing (CBS, 2011) resulting in water and environmental degradation in the major cities of Nepal (Ghimire, 1985;
Scholz, 2001; Kannel, 2007). Consequently many river sections have lost their ability of providing ecological services for the human society, e.g. self purification capacity, recreational benefits and many others (Shrestha et al, 2009). Therefore regular assessment and monitoring of rivers are essential. Since an integrated approach using biological along with traditional physical and chemical evaluations are considered the best (Reynoldson et al., 1989), such techniques are frequently used to monitor river water quality. Among the different biological indicators, macroinvertebrates are often use as they have been found to integrate and respond to the cumulative impacts of both physical and chemical disturbances (Sharma et al., 2005). This paper attempts to study the impacts of urbanization using macroinvertebrates as biological indicators in Budhi Khola and Singhya Khola of Biratnagar and Itahari in Eastern Nepal. Biratnagar and Itahari are two municipalities in the Eastern Development Region, Nepal. These two municipalities have experienced a rapid urban development in the Terai region over the years due to which there is an increasing concern of water quality deterioration. Moreover people living along the banks of these rivers are heavily dependent on the river water for various activities. Therefore the monitoring of the water quality of these rivers becomes imperative.
Material and Methods
Study AreaTwo rivers were studied during the study period, which were Singhya Khola of Biratnagar and Budhi Khola of Itahari municipality of Eastern Development Region, Nepal (Figure 1). Five sites (site 1 – site 5) from each river were identified for the study considering different effects. Site 1 is considered as reference or the condition of river water entering the municipality territory.
Budhi Khola starts from mid hills, east of Dharan, and flows through the industrial areas of Itahari. After urban area of Itahari it flows though the industrial area of Khanar, Sonapur and Duhabi, and it is also border of Hattimuda and Duhabi VDC. Singhya Khola borders the Biratnagar Municipality from the eastern side.
Figure 1 : Map of the Study Area Identification of Point Sources of Pollution
To identify the pollution source, each river was visited and visual assessment was conducted by walking along the banks of the rivers.
Physico - Chemical Analysis
Selected physico-chemical parameters such as the temperature, conductivity, pH and Dissolved Oxygen were measured in the site itself using multi parameter kits. 500 ml of water samples were collected for estimation of Biological Oxygen Demand (BOD), Nitrate, Phosphate and Ammonia. Biological Oxygen Demand
(BOD) was analyzed by Azide Modification at Water Lab, Biratnagar and Nitrate by Brucine method, Phosphate by Ammonium Molybdate method, and Ammonia by Nesslers Reagent method at NCDC water analysis lab following titration methods.
Biological Assessment Method
Qualitative sampling of macroinvertebrates was done following Barbour et al.
(1999). Macroinvertebrates were collected using hand-net with mesh size 250 µm.
A one hundred meter river stretch was sampled in each site. The substrate was disturbed by kicking action in front of the net to collect the organisms.
Macroinvertebrates were allowed to be drifted towards the net. Artificial substrates such as woods and other detritus were also inspected for macroinvertebrates. Stones were also turned and observed and some macroinvertebrates were handpicked as well. The collected specimens were sorted in a white tray and some were identified in field itself and then samples were preserved in 70 % Ethanol and brought to the laboratory for further identification.
NEPBIOS is used to classify the river water quality which consists of five classes and color codes. Macroinvertebrates were identified up to family level using relevant identification keys and literature (Merrit and Cummins, 1996; Wolfman et al. 2006 and Hartmann, 2007). An ecological assessment tool Nepalese Biotic Score/Average Score Per Taxon (NEPBIOS/ASPT) (Sharma, 1996) was applied to obtain the Water Quality Class (WQC) of the sampling sites. In this method, 82 macroinvertebrate families are assigned a numeric value (1 to 10) based on their pollution tolerance and WQC is determined by adding the total score of the animals divided by the total numbers of the groups of the animals present in the site. WQC is determined with reference to the transformation table for the NEPBIOS/ASPT values obtained.
Results and Discussion
Point Sources of Pollution at the Rivers
The main sources of pollution in both the rivers are non point sources arising from agriculture, improper sanitation, bathing and washing. S4 at Buddhi Khola was observed to be the most polluted site with multiple stressors. This site receives the highway drainage which is the main point source of sewage. The site also had a cremation site, solid waste dumping particularly at the sides of the bridge. The other stressors included sand and gravel extraction. The major points and area receiving different forms of pollution in both rivers are shown in Table 1.
Table 1 : Major pollution sources and their magnitude
Site Code Pollution Sources
B5 Highway Drainage
B3 Sand extraction activity
S2 Cremation site
S4 Solid waste disposal at the side of the bridge, on the rivers and river banks
S3 Match factory drainage
B5 Household sewage drainage
S3 Open sewage
B5 Domestic activity like bathing, washing, cattle washing, etc
Physico- Chemical Parameters
The temperature of all rivers ranged from 19 to 25°C which is normal for the low land rivers of Nepal. The temperature fluctuates very much with time and weather condition and is not considered as a major parameter for water quality assessment. In this study, all sites were with higher pH (more than 7) value which might be due to natural source (lime stone rocks) through which the water is flowing. The higher pH might also be due to anthropogenic activities like sewage discharge, mainly detergents and crimination activities (ash) also help in higher Ph. The conductivity levels of the studied river samples are between 423 to 511 S/cm, which shows that the mineral and salt content in the river water is low when compared with the WHO guidelines The BOD values for Budhi Khola is found low (less than 3 mg/L) which shows that the water is still with less external pollution. Comparatively, Singiya Khola recorded higher BOD values at site S1, S2 and S5 (higher than 10 mg/L) which are mainly due to point source pollution (see pollution and pollution source points in river section). In terms of Nitrate, Phosphate and Ammonia in studied rivers, the levels are within the guideline values. However, the disturbed and municipal discharge sites show the higher values indicating that the rivers are in threat due to human activities.
These three values are found to be increasing along with the downstream river flow in all rivers which might be due to the cumulative effect of the pollution Results of the physico- chemical parameters are given in the Table 2.
Table 2 : Result of physico-chemical analysis of Budhi and Singhya Khola.
Parameters Budhi Khola Singhya Khola
B1 23.4 S1 19.2
B2 21 S2 22
B3 21.2 S3 21
B4 22.2 S4 22.2
B5 23.2 S5 21.7
Temperature Sites
Mean (±SD) 22.2±1.1
Sites
Mean (±SD) 21.2±1.2
B1 8.2 S1 9.6
B2 9 S2 10.5
B3 9.2 S3 10.9
B4 9.3 S4 12.1
B5 11 S5 11.4
pH Sites
Mean (±SD) 9.34±1
Sites
Mean (±SD) 10.9±0.9
B1 511 S1 429
B2 440 S2 440
B3 441 S3 456
B4 442 S4 457
B5 443 S5 423
Conductivity (µS/cm) Sites
Mean (±SD) 455.4±31.1 Sites
Mean (±SD) 441±15.4
B1 6.67 S1 9.69
B2 10 S2 8.29
B3 9.85 S3 10.8
B4 10.6 S4 10.67
B5 9.5 S5 10.3
DO (mg/L) Sites
Mean (±SD) 9.93±0.8
Sites
Mean (±SD) 10.95±1
B1 2.78 S1 15.89
B2 2.94 S2 14.6
B3 2.5 S3 8.8
B4 2.54 S4 8.07
B5 4.44 S5 12.99
BOD (mg/L) Sites
Mean (±SD) 3.04±0.8
Sites
Mean (±SD) 12.07±3.4
B1 0.18 S1 0
B2 0.47 S2 0.29
B3 0.35 S3 0.41
B4 0 S4 0.18
B5 0.24 S5 0.12
Nitrate (mg/L) Sites
Mean (±SD) 0.24±0.17
Sites
Mean (±SD) 0.2±0.15
B1 0.01 S1 0.16
B2 0.06 S2 0.18
B3 0.17 S3 0.23
B4 0.23 S4 0.19
B5 0.2 S5 0.22
Phosphate (mg/L) Sites
Mean (±SD) 0.13±0.09
Sites
Mean (±SD) 0.19±0.02
B1 0.31 S1 0.13
B2 0.13 S2 0.06
B3 0.38 S3 0.06
B4 0.69 S4 0.56
B5 0.38 S5 0.69
Ammonia (mg/L) Sites
Mean (±SD) 0.37±0.2
Sites
Mean (±SD) 0.3±0.3